TAPPI T 464

Standard:

TAPPI

Method:

TAPPI T 464

Title:

Water vapor transmission rate of paper and
paperboard at high temperature and humidity

Scope

TAPPI T 464 is for the gravimetric determination of the water vapor transmission rate (WVTR) of sheet materials at 37.8°C (100°F) with an atmosphere of 90% RH on one side and a desiccant on the other. It is generally suitable for any material up to 3 mm (1/8 in.) thick, although it may be used with caution for thicker materials if the edges of the specimen are completely sealed. For testing at other conditions see TAPPI T 448 “Water Vapor Transmission Rate of Paper and Paperboard at 23°C (73°F) and at 50% RH.” This test can be used for both creased and uncreased specimens.

Significance

This method provides a means for measuring the ability of a material to protect contents, that are enclosed within the material, from undesirable changes due to the transmission of water vapor to or from the surrounding environment. The influence of temperature and humidity on the water vapor transmission rate of paper or paperboard is seldom linear, so test results obtained at lower temperatures and humidities cannot safely be extrapolated to apply to warmer, more humid conditions. If sheet materials are not homogeneous, there may be a considerable difference in the transmission rate depending on which side faces the high humidity. Usually the test is made so as to simulate the use of the material in practice; for example, a material for enclosing a dry product would be tested by exposing to the dry atmosphere that surface which would face the product in the package.

Samples

Three sheets of material are needed for the test. IPS tests for 5 days with readings taken twice a day, unless the customer specifies an alternate time frame. The customer must specify which surface is exposed to the humidity.